From Beyond The Rainbow Somewhere

COSMOLOGY

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Look on my works, ye Mighty, and despair!’ says Ozymandias’s ruined statue in the desert of Shelley’s imagination. Shelley’s sonnet is often interpreted as a sober warning that human works are fleeting, but when I read it as a young boy it kindled a sense of adventure; it suggested a wonderfully mysterious past beneath my familiar suburban surroundings. As a child, I was obsessed with archaeology, the attempt to understand the past through enigmatic remains. I spent many afternoons digging up dark patches of Midwestern soil, as I searched the region’s dense forests for artefacts of the Mississippian Indian cultures. I never found a lost city, but I occasionally turned up an arrowhead that would set me speculating about its owner and how it was lost. Through archaeology, I came to see landscapes as temporary surfaces that concealed a deep history. The world became rich with hidden texts.

Boyhood obsessions often linger into adulthood, even if they aren’t immediately recognisable. These days I find myself looking up into the Milky Way’s majestic thread, wondering if its stars play host to monuments as haunting as those found in Egypt’s Valley of the Kings. The natural sciences tell us that time is deep, and that civilisations could have arisen well before the Earth formed. Today, a small group of interstellar archaeologists is looking for evidence of those civilisations. They are tantalised by the possibility that the universe is not just a birthplace of alien cultures but also their necropolis.

We use the word ‘archaeology’ to describe this effort, because looking into deep space takes us deep into the past. The photons that strike our telescopes’ detectors take time to reach us: the light of Alpha Centauri, the nearest stellar system, is 4.3 years old when it arrives. It travels at 300,000 kilometres per second but has to cross 40 trillion kilometres to get here. Dig gradually into the soil and you push through layers accreted by wind, rain, construction, and flood. Dig deep into the sky, beyond local stars such as Alpha Centauri, and you push the clock back with the same inexorability. Epsilon Eridani, another nearby star, is seen as it was over 10 years ago. Light from the fascinating Gliese 667C, a red dwarf with three planets in its habitable zone, takes 22 years to make the journey.

In the cosmic scheme of things, these are trivial distances. Our green and blue world circles its star some 27,000 light years from the galactic centre. The glow we see at the Milky Way’s core began its voyage towards us at a time when prehistoric hunters were chasing mammoths across Europe’s ice sheets. The galaxy itself spans 100,000 light years, and its nearest equivalent, the great disc of Andromeda, is 2.5 million light years away. We see it as it looked when humanity’s ancestors walked the African savannah. When interstellar archaeologists tilt their telescopes to the sky, they are gazing into the deep history of the cosmos, but to find a civilisation more advanced than ours, they have to tilt their imaginations into the future. They have to plot out a plausible destiny for humanity, and then go looking for it in the cosmic past.

If we can so easily misinterpret our own past, how might we misconstrue the artefacts of a truly alien culture?

Conventional archaeology has shown us how difficult it is to make guesses about civilisations across time. In the late 19th century, the excavation of Hisarlik, the site in Turkey now thought to be the location of ancient Troy, soared into the European imagination through the work of Heinrich Schliemann. Legend has it that the wealthy amateur sent a cable that prematurely proclaimed: ‘I have looked upon the face of Agamemnon.’ It is not clear that he actually used those words, but we do know Schliemann’s work enchanted the salons of Europe, a continent that was besotted with the mysteries of a deeply romanticised past.

But Schliemann was hardly a professional scientist. He had made his fortune as an indigo merchant, export agent and commodities speculator before succumbing to a growing passion for all things Mycenaean. When he got to Hisarlik, he and his team unwittingly dug straight through the layer now thought to have been Homer’s Troy, compromising much of that stratum for later investigation, while uncovering decorative objects from between 300 and 500 years earlier — objects that Schliemann’s wife, a Helen in the Victorian fashion, wore when out on the town.

If we can so easily misinterpret our own past, how might we misconstrue the artefacts of a truly alien culture? One can only wonder if a modern-day Schliemann, armed with telescope or radio dish, and freighted with myriad assumptions, might not blunder away an equally enigmatic interstellar find. Interstellar archaeologists are looking for evidence of engineering on scales that dwarf our own. They assume that civilisations eventually build technologies capable of exploiting the energy resources of entire stars. They are building on the early work of the Soviet astronomer Nikolai Kardashev, who, in 1964, set about categorising these futuristic civilisations. His scheme, called the Kardashev Scale, has three types, and so far humanity does not even rate as a Type I — a civilisation that can master the energy resources of its entire planet. A Type II culture can tap all the resources of its local star, and a Type III can harness the energy of an entire galaxy. We do not, of course, know if any civilisation other than our own exists, but Kardashev’s scale offers us a way of approaching the problem of detection: it gets us thinking about what kind of traces these advanced civilisations might leave behind.

Imagining the engineering of ancient extraterrestrials is difficult work, foolhardy even. The earliest attempts to do it tended to focus on the largest conceivable structures. The former Fermilab scientist Richard Carrigan, one of interstellar archaeology’s pioneers, has long been a vocal proponent of the hunt for Dyson spheres, a technology proposed by Freeman Dyson in 1960. Dyson predicted that energy-seeking civilisations would surround their home stars in a technological shell, or a swarm of spacecraft, in order to capture its energy. A sphere with the radius of Earth’s orbit would have an interior surface area 100 million times as large as the surface area of our planet. In 1966, Carl Sagan suggested that such spheres might be detectable, but he cautioned that they would be hard to distinguish from natural objects that gave off a similar infrared signature. Decades later, Carrigan would tell New Scientist that he wanted to try anyway, that he ‘wanted to get into the mode of the British Museum, to go and look for artefacts’.

True to his word, Carrigan has conducted a series of searches for Dyson spheres, following earlier work by the Russian astronomers Vyacheslav Ivanovich Slysh and MY Timofeev. Carrigan combed IRAS, the infrared sky survey that dates back to the 1980s, looking for the distinct infrared signatures calculated for this purely theoretical technology. More recently, Berkeley’s well known exoplanet hunter Geoff Marcy began studying 1,000 Milky Way star systems for evidence of large structures, looking for visible disturbances in light levels around the parent star as the techno-structures transit between their star and the Earth. At Penn State, Jason Wright and his colleagues Matthew Povich and Steinn Sigurðsson are pushing the search for Dyson spheres deeper into the galaxy, and even beyond it, by examining infrared data from the Wide-field Infrared Survey Explorer (WISE) and the Spitzer Space Telescope. Wright’s group is also looking for ‘Fermi bubbles’, patches of a galaxy that show higher infrared emissions than the rest, which could be a sign that a civilisation is gradually transforming a galaxy as it works its way across it. M51, the ‘Whirlpool’ galaxy, offers a good field for study, because it is turned so that we see it face-on.

In the age of big data, it is possible that evidence of an extraterrestrial civilisation is already hiding in our archives

None of the ongoing interstellar archaeology searches will be easy to confirm, supposing they find something notable, for natural explanations for such phenomena abound. For one, spiral galaxies already contain voids that can mimic a civilisation’s spread. The galaxy VIRGOHI21 is a good example. At optical wavelengths, it’s dark enough to suggest it might be a candidate for Dyson-style engineering. But HI21 is also explained through the effects of so-called ‘tidal shredding’, a natural process that may be producing the same signature. Dyson sphere signatures are trickier still: they could be nothing more than stars enshrouded in dust clouds. Positive results turned up by interstellar archaeologists will need plenty of scrutiny.

The field’s deeper thinkers are starting to wonder if there might be other ways to search. Milan Ćirković, from the Astronomical Observatory of Belgrade, has suggested we go after large artificial objects in transiting orbits. He says we ought to look for something like the huge space colonies once championed by Gerard O’Neill, structures that could be involved in large-scale industrial operations, which might be furnaces for antimatter. If so, their existence could be confirmed by the detection of unusual gamma ray signatures. Alien engineers might even manipulate their own central star. In 1957, Fritz Zwicky suggested that civilisations could fire fuel pellets into their local stars, to move their solar systems to new locations, especially when interstellar dangers loomed. Forty years later, the physicist Leonid Shkadov suggested that huge spherical mirrors could be built to accomplish the same thing, by creating a feedback effect from the star’s radiation, that would let its creators control the star’s trajectory through the galaxy.

Interstellar archaeologists are forced to wonder what structures like these might look like from a distance of thousands or tens of thousands of light years. Fortunately, they can tinker with different signatures, because we already have a vast trove of star data to trawl. With detailed information on billions of systems sitting on our servers, and processing power whose growth shows no signs of slowing, we can tune our algorithms to search for transit signatures that could flag engineering projects of immense scale. In the age of big data, it is possible that evidence of an extraterrestrial civilisation is already hiding in our archives.

Our searches might even turn up a galactic gravestone, a monument meant to record the wonders of a dying civilisation for posterity. Luc Arnold from the Aix Marseilles Université has suggested that distant civilisations might use planet-sized objects as deliberate celestial signs, knowing that their signature could be readily detected by alien astronomers. Such objects might be the final act of a civilisation in its death throes, left behind as a legacy to surviving cultures. The astronomer Charles Lineweaver has pointed out that most of our galaxy’s terrestrial-class worlds are two billion years older than Earth. How many civilisations have flourished and died out in that time?

Of course the search for the remnants of these civilisations need not stop with unusual light signatures. In addition to energy, an ancient spacefaring culture would need large amounts of raw material to build its structures. Working with Martin Elvis of the Harvard Smithsonian Center for Astrophysics, the astronomer Duncan Forgan has investigated the possibility that the debris discs around other stars could show signs of large-scale asteroid mining. Rock and ice debris is concentrated in our own solar system at various distances, from the main-belt asteroids between Mars and Jupiter to the Kuiper Belt and the still more distant Oort Cloud. And we now have unambiguous evidence of similar discs of debris around stars such as Vega, Fomalhaut and Beta Pictoris.

Asteroid mining could show up in our telescopes as chemical imbalances in these discs. If we were to see a sharp depletion of elements like iron and nickel, or rare elements, such as platinum and palladium, that might flag extraterrestrial mining operations. The dynamics of the debris disc itself would likewise be affected, as larger objects were broken down for industrial use. The production of dust through mining process might also cause unusual temperature gradients. We don’t have the equipment to make these measurements at present, but future space-based observatories may be able to.

And what of stars that are anomalous such as the ‘blue straggler’ stars that seem much younger than the stars around them? Astronomers are puzzled by them because globular clusters — ancient cities of stars that sit in a spherical halo around the Milky Way — are where blue stragglers were first identified, and these are thought to contain stars that formed at the same time. Now we’re finding blue stragglers in the galactic bulge itself, another unusual place for younger stars since most star formation there has stopped. The giant blue stars we see shining there should have exploded into supernovae billions of years ago.

There are many theories that attempt to explain the blue straggler phenomenon, but only one implicates interstellar archaeology. Martin Beech, an astronomer at the University of Regina in Saskatchewan, has suggested that we consider blue stragglers candidates for follow-up searches to the Search for Extraterrestrial Intelligence (SETI). There are scenarios in which you could imagine a sufficiently advanced civilisation decided to adjust its own star’s ageing process. Pump enough shell hydrogen back into the inner core of a star and you should be able to prolong its lifetime, thus preserving any culture that lives in the vicinity. Beech thinks blue stragglers could mark a Kardashev Type II culture trying to preserve its habitat.

All of these searches ask us to put ourselves in the minds of beings about whom we know absolutely nothing. The physicist David Deutsch has flagged this as a problem for prediction of all kinds, not just those involving SETI. According to Deutsch, we can distinguish between ‘prophecy’ and ‘prediction’, with prophecy being the discussion of things that are not knowable, while prediction deals with conclusions that are based on good explanations of the universe. As prognosticators from Thomas Malthus to the Club of Rome have demonstrated, we may be able to identify problematic trends in the present that can be extended into the future, but we cannot know what knowledge we will acquire in the future to manage those problems. This is why no scientific era has succeeded in imagining its successor. The scientists of the late 19th century discovered this firsthand, when confronted with the emergence of quantum theory and relativity early in the early 20th. Both theories raised questions earlier theorists couldn’t have even formulated.

In the context of interstellar archaeology, the problem is that we have no analogues in our experience for what advanced cultures might create. Patience is the byword as the effort proceeds, the same patience that Heinrich Schliemann’s successors have used to master the art of sifting through rubble, with careful digging and delicate brushwork sweeping aside soil to uncover the shape of a fragmentary artefact. Interstellar archaeologists are tasked with sifting through gigabytes of data, not layers of soil, but the principle is the same. In a recent paper with Robert Bradbury and George Dvorsky, Milan Ćirković offered a paradigm for a new SETI, one that would include not only searches like these but a wide range of ‘future studies’ that would encompass how a post-biological intelligence might emerge and make itself known — intentionally or unintentionally.

This approach asks interstellar archaeologists to expand their field to include the study of computer science, artificial life, evolutionary biology, the philosophy of mind and the evolving science of astrobiology. A successful search for macro-engineering would challenge us to re-imagine our position in the cosmos, confronting us with structures that might identify a living culture, or one long dead. In this respect the interstellar archaeologists are like the Anglo-Saxon and Celtic peoples who inhabited Britain after the end of the Roman occupation. They found themselves living amid engineering that was beyond their own capabilities, a disquieting experience that made its way into Anglo-Saxon poems such as ‘The Ruin’:

The city buildings fell apart, the works

Of giants crumble. Tumbled are the towers

Ruined the roofs, and broken the barred gate,

Frost in the plaster, all the ceilings gape,

Torn and collapsed and eaten up by age.

And grit holds in its grip, the hard embrace

Of earth, the dead-departed master-builders,

Until a hundred generations now

Of people have passed by. Often this wall

Stained red and grey with lichen has stood by

Surviving storms while kingdoms rose and fell.

And now the high curved wall itself has fallen.

Verse like this infuses our past with grandeur while imbuing its artefacts with the rich patina of shared human experience. It serves as a connective tissue between cultures. But no such collective history can illuminate the discoveries of our interstellar archaeologists. Finding the monuments of civilisations more advanced than our own would challenge us to place ourselves in a totally unfamiliar context, as cosmic newcomers who can suddenly aspire to long lifetimes. If we found a lost city in the sky, it might fire our imaginations. It might give us reason to think we’ll outlast existential threats like nuclear weapons and biological terrorism. An interstellar Hisarlik would tell us that some civilisations do survive these dangers and learn to harness immense energies to grow. Rather than despair, we may see their mighty works and rejoice at what we can become.

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Humans have known about the force of gravity since ancient times. Yet, we are still exploring its true nature, how it works, and why it works the way it does.

Haaaaaaaaaaaave you met PSR B1913+16? The first three letters of its name indicate it’s a pulsating radio source, an object in the universe that gives off energy as radio waves at very specific periods. More commonly, such sources are known as pulsars, a portmanteau of pulsating stars.

When heavy stars run out of hydrogen to fuse into helium, they undergo a series of processes that sees them stripped off their once-splendid upper layers, leaving behind a core of matter called a neutron star. It is extremely dense, extremely hot, and spinning very fast. When it emits electromagnetic radiation in flashes, it is called a pulsar. PSR B1913+16 is one such pulsar, discovered in 1974, located in the constellation Aquila some 21,000 light-years from Earth.

Finding PSR B1913+16 earned its discoverers the Nobel Prize for physics in 1993 because this was no ordinary pulsar, and it was the first to be discovered of its kind: of binary stars. As the ‘B’ in its name indicates, it is locked in an epic pirouette with a nearby neutron star, the two spinning around each other with the orbit’s total diameter spanning one to five times that of our Sun.

Losing energy but how?

The discoverers were Americans Russell Alan Hulse and Joseph Hooton Taylor, Jr., of the University of Massachusetts Amherst, and their prize-winning discovery didn’t culminate with just spotting the binary pulsar that has come to be named after them. They found that the pulsar’s orbit was shrinking, meaning the system as a whole was losing energy. They found that they could also predict the rate at which the orbit was shrinking using the general theory of relativity.

In other words, PSR B1913+16 was losing energy as gravitational energy while proving a direct (natural) experiment to verify Albert Einstein’s monumental theory from a century ago. (That a human was able to intuit how two neutron stars orbiting each other trillions of miles away could lose energy is homage to the uniformity of the laws of physics. Through the vast darkness of space, we can strip away with our minds any strangeness of its farthest reaches because what is available on a speck of blue is what is available there, too.)

While gravitational energy, and gravitational waves with it, might seem like an esoteric concept, it is easily intuited as the gravitational analogue of electromagnetic energy (and electromagnetic waves). Electromagnetism and gravitation are the two most accessible of the four fundamental forces of nature. When a system of charged particles moves, it lets off electromagnetic energy and so becomes less energetic over time. Similarly, when a system of massive objects moves, it lets off gravitational energy… right?

“Yeah. Think of mass as charge,” says Tarun Souradeep, a professor at the Inter-University Centre for Astronomy and Astrophysics, Pune, India. “Electromagnetic waves come with two charges that can make up a dipole. But the conservation of momentum prevents gravitational radiation from having dipoles.”

According to Albert Einstein and his general theory of relativity, gravitation is a force born due to the curvature, or roundedness, of the space-time continuum: space-time bends around massive objects (an effect very noticeable during gravitational lensing). When massive objects accelerate through the continuum, they set off waves in it that travel at the speed of light. These are called gravitational waves.

“The efficiency of energy conversion – from the bodies into gravitational waves – is very high,” Prof. Souradeep clarifies. “But they’re difficult to detect because they don’t interact with matter.”

Albie’s still got it

In 2004, Joseph Taylor, Jr., and Joel Weisberg published a paper analysing 30 years of observations of PSR B1913+16, and found that general relativity was able to explain the rate of orbit contraction within an error of 0.2 per cent. Should you argue that the binary system could be losing its energy in many different ways, that the theory of general relativity is able to so accurately explain it means that the theory is involved, and in the form of gravitational waves.

Prof. Souradeep says, “According to Newtonian gravity, the gravitational pull of the Sun on Earth was instantaneous action at a distance. But now we know light takes eight minutes to come from the Sun to Earth, which means the star’s gravitational pull must also take eight minutes to affect Earth. This is why we have causality, with gravitational waves in a radiative mode.”

And this is proof that the waves exist, at least definitely in theory. They provide a simple, coherent explanation for a well-defined problem – like a hole in a giant jigsaw puzzle that we know only a certain kind of piece can fill. The fundamental particles called neutrinos were discovered through a similar process.

These particles, like gravitational waves, hardly interact with matter and are tenaciously elusive. Their discovery was predicted by the physicist Wolfgang Pauli in 1930. He needed such a particle to explain how the heavier neutron could decay into the lighter proton, the remaining mass (or energy) being carried away by an electron and a neutrino antiparticle. And the team that first observed neutrinos in an experiment, in 1942, did find it under these circumstances.

Waiting for a direct detection

On March 17, radio-astronomers from the Harvard-Smithsonian Centre for Astrophysics (CfA) announced a more recent finding that points to the existence of gravitational waves, albeit in a more powerful and ancient avatar. Using a telescope called BICEP2 located at the South Pole, they found the waves’ unique signature imprinted on the cosmic microwave background, a dim field of energy leftover from the Big Bang and visible to this day.

At the time, Chao-Lin Kuo, a co-leader of the BICEP2 collaboration, had said, “We have made the first direct image of gravitational waves, or ripples in space-time across the primordial sky, and verified a theory about the creation of the whole universe.”

Spotting the waves themselves, directly, in our human form is impossible. This is why the CfA discovery and the orbital characteristics of PSR B1913+16 are as direct detections as they get. In fact, finding one concise theory to explain actions and events in varied settings is a good way to surmise that such a theory could exist.

For instance, there is another experiment whose sole purpose has been to find gravitational waves, using laser. Its name is LIGO (Laser Interferometer Gravitational-wave Observatory). Its first phase operated from 2002 to 2010, and found no conclusive evidence of gravitational waves to report. Its second phase is due to start this year, in 2014, in an advanced form. On April 16, the LIGO collaboration put out a 20-minute documentary titled Passion for Understanding, about the “raw enthusiasm and excitement of those scientists and researchers who have dedicated their professional careers to this immense undertaking”.

The laser pendula

LIGO works like a pendulum to try and detect gravitational waves. With a pendulum, there is a suspended bob that goes back and forth between two points with a constant rhythm. Now, imagine there are two pendulums swinging parallel to each other but slightly out of phase, between two parallel lines 1 and 2. So when pendulum A reaches line 1, pendulum B hasn’t got there just yet, but it will soon enough.

When gravitational waves, comprising peaks and valleys of gravitational energy, surf through the space-time continuum, they induce corresponding crests and troughs that distort the metrics of space and passage of time in that area. When the two super-dense neutron stars that comprise PSR B1913+16 move around each other, they must be letting off gravitational waves in a similar manner, too.

When such a wave passes through the area where we are performing our pendulums experiment, they are likely to distort their arrival times to lines 1 and 2. Such a delay can be observed and recorded by sensitive instruments.

Analogously, LIGO uses beams of light generated by a laser at one point to bounce back and forth between mirrors for some time, and reconvene at a point. And instead of relying on the relatively clumsy mechanisms of swinging pendulums, scientists leverage the wave properties of light to make the measurement of a delay more precise.

At the beach, you’ll remember having seen waves forming in the distance, building up in height as they reach shallower depths, and then crashing in a spray of water on the shore. You might also have seen waves becoming bigger by combining. That is, when the crests of waves combine, they form a much bigger crest; when a crest and a trough combine, the effect is to cancel each other. (Of course this is an exaggeration. Matters are far less exact and pronounced on the beach.)

Similarly, the waves of laser light in LIGO are tuned such that, in the absence of a gravitational wave, what reaches the detector – an interferometer – is one crest and one trough, cancelling each other out and leaving no signal. In the presence of a gravitational wave, there is likely to be one crest and another crest, too, leaving behind a signal.

A blind spot

In an eight-year hunt for this signal, LIGO hasn’t found it. However, this isn’t the end because, like all waves, gravitational waves should also have a frequency, and it can be anywhere in a ginormous band if theoretical physicists are to be believed (and they are to be): between 10-7 and 1011 hertz. LIGO will help humankind figure out which frequency ranges can be ruled out.

In 2014, the observatory will also reawaken after four-years of being dormant and receiving upgrades to improve its sensitivity and accuracy. According to Prof. Souradeep, the latter now stands at 10-20 m. One more way in which LIGO is being equipped to find gravitational waves is by created a network of LIGO detectors around Earth. There are already two in the US, one in Europe, and one in Japan (although the Japanese LIGO uses a different technique).

But though the network improves our ability to detect gravitational waves, it presents another problem. “These detectors are on a single plane, making them blind to a few hundred degrees of the sky,” Prof. Souradeep says. This means the detectors will experience the effects of a gravitational wave but if it originated from a blind spot, they won’t be able to get a fix on its source: “It will be like trying to find MH370!” Fortunately, since 2010, there have been many ways proposed to solve this problem, and work on some of them is under way.

One of them is called eLISA, for Evolved Laser Interferometer Space Antenna. It will attempt to detect and measure gravitational waves by monitoring the locations of three spacecraft arranged in an equilateral triangle moving in a Sun-centric orbit. eLISA is expected to be launched only two decades from now, although a proof-of-concept mission has been planned by the European Space Agency for 2015.

Another solution is to install a LIGO detector on ground and outside the plane of the other three – such as in India. According to Prof. Souradeep, LIGO-India will reduce the size of the blind spot to a few tens of degrees – an order of magnitude improvement. The country’s Planning Commission has given its go-ahead for the project as a ‘mega-science project’ in the 12th Five Year Plan, and the Department of Atomic Energy, which is spearheading the project, has submitted a note to the Union Cabinet for approval. With the general elections going on in the country, physicists will have to wait until at least June or July to expect to get this final clearance.

Once cleared, of course, it will prove a big step forward not just for the Indian scientific community but also for the global one, marking the next big step – and possibly a more definitive one – in a journey that started with a strange pulsar 21,000 light-years away. As we get better at studying these waves, we have access to a universe visible not just in visible light, radio-waves, X-rays or neutrinos but also through its gravitational susurration – like feeling the pulse of the space-time continuum itself.

Scientists have uncovered a new key to understanding the strange workings of neutron stars — objects so dense they pack the mass of multiple suns into a space smaller than a city.

It turns out there is a universal relationship linking a trio of properties related to how fast the star spins and how easily its shape deforms. This relationship could help astronomers understand the physics inside neutron stars’ cores, and distinguish these stars from their even weirder cousins, quark stars.

Neutron stars are born when massive stars run out of fuel for nuclear fusion and collapse. They expel their outer layers, and their cores fall inward under the pull of gravity to become denser and denser. Eventually, the pressure is so great that even atoms cannot retain their structure, and they collapse. Protons and electrons essentially melt into each other, producing neutrons as well as lightweight particles called neutrinos. The end result is a star whose mass is 90percent neutrons. [Graphic: Inside a Neutron Star]

Quark stars are bizarre theorized objects that are even denser than neutron stars, where even neutrons can’t survive and they melt down into theirconstituent quarks.

“Quark stars haven’t been observed,” said Nicolas Yunes, a physicist at Montana State University who co-authored the new study with his Montana State colleague Kent Yagi. Their paper was published online today (July 25) in the journal Science.

Part of the problem is that scientists can’t definitively tell the difference between neutron stars and quark stars from current observations, so some of the known neutron stars might actually be quark stars. However, the new relationship found by Yagi and Yunes could help distinguish the two super-dense bodies.

The researchers discovered that for all neutron stars there is a relationship between three quantities: a star’smoment of inertia, which defines how quickly it can spin, and its Love number and quadrupolemoment, which reflect how easily the star’s shape deforms. The newfound relationship means that if one of these quantities can be measured, the others can be deduced.

Though scientists previously understood that these properties were connected, they didn’t realize that such a standard relationship held true. It turns out to be similar to a relationship known for black holes, which are even denser than neutron and quark stars.

“For black holes there is a well-known definite relation, but that made sense because black holes don’t have internal structure,” Yunes told SPACE.com. “We all expected that that wouldn’t be true once you have objects that do have structure.”

Understanding this relationship for neutron stars could also help scientists study general relativity and the laws of physics in a strong gravitational field.

“Since a neutron star is very compact, it offers us a nice test-bed to probe gravitational theory in the strong-field regime,” Yagi told SPACE.com via email. Previously, uncertainties about the internal structure of neutron starsprevented researchers from carrying out such tests, he added.

“However, since our universal relations do not depend on the neutron star internal structure, one can perform general relativity tests without being affected by the ignorance of the internal structure,” Yagi said.

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A new study finds human sleep patterns are timed to the phases of the moon.

If you have trouble falling asleep around the same time each month, the moon might be to blame.

Scientists say they’ve found evidence that human sleep patterns are timed to the phases of the moon, and that people sleep 20 minutes less on average during a full moon.

“The lunar cycle seems to influence human sleep, even when one does not ‘see’ the moon and is not aware of the actual moon phase,” study co-authorChristian Cajochen, a chronobiologist at the University of Basel in Switzerland, said in a statement.

Cajochen says his team’s findings, detailed in the July 25 issue of the journalCurrent Biology, could be evidence of a biological “circalunar clock” ticking inside of humans.

Similar to the circadian clock that helps humans and other animals sync their physical and behavioral changes to a 24-hour day-night cycle, a circalunar clock would somehow be synchronized with the changing phases of the moon.

Evidence of a circalunar clock has been found in insects and reptiles, but not yet in humans. Cajochen stressed that there could be other ways to explain his findings.

“This is just an interpretation of the results,” he said in an interview Thursday.

Malcom von Schantz, a sleep and circadian researcher at the University of Surrey in the U.K., called the new findings “fascinating” because they run counter to the results of several other studies that failed to find a link between the moon and human behavior.

“Essentially, every report published to date has failed to show significant associations between the phase of the moon and any number of behavioral and physiological parameters,” von Schantz, who was not involved in the study, said in an email.

“This is the very first report that suggests an association with one behavior, sleep, and of course it’s a behavior that in our species normally occurs at night.”

Unrestful Sleep

In their new study, Cajochen and his team studied 33 volunteers in the lab while they slept. While they slept, the subjects’ brain patterns, eye movements, and hormone secretions were monitored.

The analysis showed that around the full moon, the volunteers slept less and their brain activity related to deep sleep dropped by 30 percent.

They also took about five minutes longer to fall asleep and showed diminished levels of melatonin, a hormone known to regulate sleep and wake cycles.

The study participants also reported feeling that their sleep was poorer when the moon was full.

The volunteers’ sleep patterns were originally studied as part of another research project, and the effects of the moon were not analyzed until much later.

“We just thought of it after a drink in a local bar one evening at full moon, years after the [original] study was completed,” the authors write.

This fact makes it difficult to come up with alternative explanations for the findings, von Schantz said.

“The subjects were sleeping in windowless rooms, and although they may have been aware of the phases of the moon, neither they nor even the investigators knew that lunar phase would be a parameter that would be considered in the study,” he added.

Kristin Tessmar-Raible, a sleep researcher at the University of Vienna in Austria, agreed. “This pretty convincingly excludes possible biases … At the present time their explanation is at least the most plausible one,” said Tessmar-Raible, who also did not participate in the research.

Ancient Roots?

Cajochen said that the circalunar rhythm in humans could be a relic from a past in which the moon could have synchronized our ancestors’ behaviors for reproduction or other purposes.

For example, Cajochen said, early humans might have been primed to sleep lightly during the full moon, “when there is more light at night and potential danger from predators is more likely.”

The origins of our circalunar clock might be far older, dating back to the very dawn of mammals, von Schantz speculated. “We have to remember that mammals evolved through what is called the nocturnal bottleneck. When dinosaurs roamed the Earth by day, the night represented a window of opportunity for a new group of vertebrates to evolve,” von Schantz said.

If humans do possess a circalunar clock, then a major unanswered question is the external cue that allows it to stay in sync with the moon, scientists say.

“Just like the circadian clock, [the circalunar clock] will need to be reset based on external time cues to stay in sync. Now what I can’t get my head around is, what would that cue be?” von Schantz said.

“It is hard to imagine that our light receptors are able to specifically filter out the light from a full moon amongst all the other light signals we receive today. We are not physically exposed to tides. And the gravitational pull of the moon is really quite weak …

“This study identifies a lot of fascinating questions for further investigations.”

Like this:

NASA hasn’t been bashful about updating the world with the findings of the Curiosity rover currently exploring Mars.

Since Curiosity landed back in August 2012, we’ve gotten plenty of updates on the progress of the mission, whether they were worthwhileor not.

There has been little success in finding actual Martian organic material during Curiosity’s expedition, butsome of the findings seemed to show the potential for organic life on Mars did at one time exist.

On Tuesday, NASA revealed a startling new discovery, which further proved that at one time, Mars was perfectly suitable for living organisms.

The answer is yes

This latest breakthrough was found in a new rock sample collected by Curiosity, which contained several of the key elements necessary for life.

Scientists were able to find sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon in powder cultivated from sedimentary rock near an ancient stream bed in the Gale Crater.

“A fundamental question for this mission is whether Mars could have supported a habitable environment,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program at the agency’s headquarters in Washington.

“From what we know now, the answer is yes.”

The analyzed data showed the area Curiosity was currently exploring could have at one time been the end of an ancient river or a wet lake bed, both of which would have provided the proper growing environment for microbes.